Data translation device for flight simulation



Nov. 28, 1950 D. H. EwxNG DATA TRANSLATION DEVICE FOR FLIGHT SIMULATION Original Filed April 30, 1948 l .Wm m l, s Kv im n s Ydr/ l Patented Nov. 28, 1950 lDATA ranNsLArioN Dui/ICE vvon FLIGHT SIMUL-.e'rloN Douglas H. Ewing, 4Chevy Chase, Md., assignor to Radio Corporation of America, a corporation of Delaware Original application April 30, 1948, `Serial' o.-

Divided and this application January 31, 1949, Serial No. 73,753

(Cl. 23S- 61) 4 Claims. l

Thisapp-lication is a division of my co-pending application U. S. Serial No. 24,155, filed April 3.0, 1948.

This invention relates generally to the vrepresentation andcontrol ofair traflic, and more particularly to improvements in the art of simulating or depicting the llightof an aircraft.

The principal object ci the invention is to provide methods and means for converting continuously one type of representation of ilightinto another type of representation. For example, the ight of an aircraft can be defined in terms of its starting point (or its position at a certain instant), its ground speed, and heading. The same information can be presented in an entirely different form, such as the direction and radial distance of the craft from a reference point. The latter'form of presentation is that ordinarily provided by ground-based radar equipment. The former is similar to that obtained on the aircraft by navigational means.

It is a specific object of the invention to provide ysystems for converting one of the abovedescribed vforms of presentation to the other.

Another object of the invention is to provide systems of the above-described type in which the necessary computations are eiected by electrical means, wherein quantities such as speed, distance, and angles are represented by corresponding Voltages.

A further object of the present invention ,is to provide systems of the described type which are simple to design and construct, and rapid and accurate in operation.

The invention will be described with reference to the accompanying drawing, wherein:

Figure 1 is a diagram illustratingthe geometry which relates the two above-described forms `of presentation,

Figure 2 is a schematic diagram of a system converting ground speed and heading information to .range and azimuth, i. e., distance and direction information, and

'Figure 3 is a schematic diagram cfa system involving `the same principles as that of Figure 2 for-converting range and azimuth information .to groundspeed and heading information.

Refer to Figure 1. It is assumed that an aircraft is at present at the position represented by the point P. The point O is a reference point suchas the location of a ground-based radar station, .and .the line N-S isa directional reference line Asuch as the local meridian through the point O.

The .position of the-craft at .the l.point P isdenoted, in polar coordinates referred to the point O, by the range or distance R and the azimuth or direction 0. The ground speed of the craft is designated by the vector VG; the direction of the vector referred to that of the line N-S is the heading, a.

If the range R0 andrazimuth 0o at some particular instant are known or assumed, and the ground speed VG and heading a are available continuously, the range R and azimuth 0 at any other instant can be determined, IThe system of Figure 2 provides range and azimuth information continuously in response tocontinuous ground speed and heading inf orma-tion.

A source l of substantially constant voltage is connected to a pair of adjustable voltage dividers 3 and 5, as shown in Figure 2. The movable arms of the voltage dividers 3 and 5 are ganged together, as indicated by the dash line l, for adjustment by means of a manually operable knob s. A pointer l i cooperates with a scale I3 to indicate the adjustment of the voltage dividers in terms of units of ground speed, such as miles per hour.

The movable arms of the Voltage dividers 3 and5 are connected to respective terminals of a component solver device i 5. The device i5 in.- cludes a sine card potentiometer, comprising a flat resistor element il and a pair of slidable contacts IS and 2! in engagement therewith. The terminals of the resistor element il' are those which are connected to the voltage dividers 3 and 5.

The contacts It and '2i are supported at right angles to ,each other on .an insulating member 23 which is rotatable by means oi a shaft 25. The shaft k25 is connected to a knob 2l provided with a pointer and scale 2% calibrated in angular measure, such as degrees. 'The resistor element il v,is also rotatable about the same axis as the shaft 25, being supported upon a gear wheel Si.

The contact I9 is connected to the input circuit of a motor control amplifier 33, which, in turn, is connected to a reversible motor 35. The amplier 33 and the motor 35 are arranged so that the motor 35 will run in a direction which depends .on the Vpolarity of the input to the amplifier 33 and at a speed which is proportional to the voltage applied to the input terminals oi the ampliiier 33. This may be Aaccomplished in any of several ways known to those skilled in the art; for example, the amplifier v33 may be a D.C. amplier, and the motor 35 may be a separately excited or vpermanent Imagnet field type device. Various known fexpedients may be .employed to assalto Y to a clearl understanding of the present invention,

it need not be described in further detail.

The contact 2i of the component resolver device l is connected to a network including a variable resistor 3l and a fixed resistor 39. The movable arm of the resistor 3i is coupled to a shaft 65. The resistor 39 is connected to the input terminals of a motor control amplier @3, which is similar to the amplifier 33 and is similarly connected to a reversible motor 45.

The output shaft il of the motor i5 is coupled through differential gearing 9 to an indicator 5I, Which is calibrated in angular terms, such as degrees. The differential 49 is arranged to enable the indicator shaft 53 to be adjusted with respect to the motor shaft di by means of a hand wheel 55. The indicator shaft 53 is coupled, as indicated by the dash line 51 to a pinion 59 which engages the gear Wheel 3 l A suitable gear ratio is provided in the coupling between the shaft 53 and the pinion 55 tc'make the angular rotations of the gear 3i and the shaft 53 equal.

Ihe shaft il of the motor 35 is coupled through differential gearing El to an indicator 63 calibrated in units of distance, such as miles. The differential 5l is arranged like the differential i9 toallow the indicator shaft 65 to be displaced with respect to the motor shaft lll by rotations of a hand wheel 51.

In the operation of the above-described system, it is arbitrarily assumed that a certain number of volts represents a ground speed of a certain number of miles per hour. Thus, the quantity miles per hour per volt may be considered as a scale factor of the equipment.

Owing to the connections between the voltage dividers 3 and 5 and the source l, one movable arrn is at a, potential positive with respect to ground and the other movable arm is at an equal potential negative With respect to ground. Thus, the voltage across the resistance element Il is symmetrical with respect to ground and has a magnitude depending upon the adjustment of the knob 9.

.ie potential with respect to ground at the contact I9. is proportional to the cosine of the angle between said contact and the longitudinal axis (represented by the arrow t9) of the card Il. With the parts in the position shown in Figure 2, said angle is substantially 90 degrees, and the potential at the contact IS is substantially aero. if either part of the component solver rotated with respect to the other, the potential with the contact is will vary according to the cosine of the angle of rotation.

Similariy, the potential at the contact 2i is proportional to the sine of the angle ,6. Assuming that the shaft 25 is rotated clockwise from its VG cos (a-a) This is the radial component of the ground speed Vector VG (Figure 2) and is actually the rate of change of distance of the aircraft from the refl erence point O.

Since the motor 35 runs at a speed which is proportional to the rate of change of the range R, the total rotation of its shaft fl! is proporional to the total change in R, and the indication displayed. on the indicator S3 changes accordingly. In order for the indicator 63 to show the true distance of the aircraft from the reference point, it must be initially adjusted by means of the hand wheel t? to show Ro, the value of R at the point where the craft is located when the operation of the equipment is started.

The potential at the contact 2i of the device 5 is proportional to:

VG sin (ai-0) This quantity is the tangential component of the ground speed VG. This voltage is divided by a quantity proportional to R, by means of the voltage divider network Which includes the resistor 3i which varies as a function of R. Thus, the voltage applied to the input terminals of the motor control amplifier 43 is proportional t0:

v2? sin (zz-47) This quantity is the rate of change of the azimuth angle 0.

The motor d5 rotates at a speed corresponding to said rate and, consequently, turns the shaft Il? through a total angle equivalent to the total change in 0. The azimuth 6o, corresponding to the position of the aircraft when the operation of the system is started, is introduced by means of the hand wheel 55 so that the indicator 5I will subsequently indicate the true value of 0, as referred to the line N--S in Figure 1.

Since the gear 3l is driven from the shaft 53 as described above, the angle (l1-0) will be maintained between the parts of the resolver i5, regardless of the variation of 6.`

Any changes in ground speed or heading during operation of the system may be inserted by corresponding adjustment of the knobs 9 and 2l'. The equipment will function continuously to indicate at all times the position of the aircraft in terms of R and 0 referred to the point O. It will be apparent without illustration that the shafts 35 and 53 may be used to drive other indicating mechanism, for example, a crab, such as is used with pilot training devices to plot a graph of the simulated course followed.

Also, it is within the contemplation of the present invention that the ground speed and heading information may be applied to the system by rotation of the shafts i and 25 automatically by measuring instruments or the like, rather than manually.

The system of Figure 3 produces the operational steps of the system of Figure 2 substantially in reverse, providing ground speed and heading information continuously in response to n output corresponding to the rate of change of' Thus, when the range R is increas-v the range.

ing, the output of the generator 11 Will be of one polarity arbitrarily designated as positive,

assaiso- 5, andwhen `the range is decreasing, theoutput of the generator 1l willbe the opposite polarity The generator 'l1 may be a permanent magnet eld device, such as a tachometer generator orany other known means functioning as described. The azimuth knob 13 is similarly coupled toa shaft'lS` driving a rate generator 8| which provides an output having a'magnitude and polarity corresponding to the rate of change of azimuth. The output of the generator 8| is applied to a voltage divider 83 whose movable contactis coupled to the range shaft 15, as indicated by the dash line 85.

The movable contact of the voltage divider 83 is coupled to a modulator 81. The rate generator `-is coupled directly to a similar modulator 89; Both modulators 8? and 89 are excited by means of an oscillator 9| which may operate at any suitable frequency, for example, 400 cycles per second. The outputs of the modulators 8'1 and 89 are coupled to respective sets of terminals of a component reso1ver'93. The compo nent'resolver 93 includes orthogonally disposed stator'windings 95 and 91 connected respectively to the modulators 81 vand 89 and orthogonally disposed rotor windings 59 and l0 I. The rotor Winding'll is connected to an A.C. voltmeter |83 calibrated in terms of ground speed (miles per hour). The rotor winding 99 is connected to a motor control circuit |85.

The motor control circuit |85 may be a balanced demodulator which provides an output having a magnitude proportional to the input thereto from the winding 99, and a polarity which depends upon the phase relationship between this 'input and a reference phase input. The

second input to the motor control circuit ISE is supplied by the oscillator 9|. The output of thecircuit `|5 energizes a reversible motor |01.

The output shaft HB8 of the motor |81 is coupledto the rotor of the component resolver 93. The shaft |639 is also coupled to one side of a differential gear mechanism The other side of the gear ||iV is lcoupled'to the azimuth shaft '13, as indicated by the dash line I I3. The spider of the differential li l is coupled to an indicator calibrated in terms of azimuth (degrees). `In lthe operation of the system of Figure 3, the rate generator 'Vl provides an output voltage proportional to the rate of Vchange of range,

@e dt Thisqu-antity is the radial component VG cos (a-) of the ground speed VG.

The rate generator 3| provides an output voltage proportional to the rate of .change of azimuth,

This .quantity is the tangential component VG Sin (a-) of the ground speed VG.

The modulators 89 and 81 are controlled by the respective rate-proportional inputs and by the 400-cycle oscillator 9| to provide 40G-cycle output voltages whose amplitudes are proportional respectively to VG cos (OL-0) and to VG sin (a-) The direction of the resultant eld, referred to the axis of the winding 91, is:

The voltage induced by said field in the rotor winding 99 depends upon the angular position of said winding. As long as there is any such voltage, the motor control circuit '|85 is actuated to energize the motor |01 to drive the rotor toward a position such that the winding 9S is perpendic ula-r to the resultant 'eld of the stator Windings. When the rotor is in this position, no

voltage is induced in the winding 99 'and the motor stops. A maximum voltage, proportional to the amplitude of the resulting stator field and thus proportional to VG, is induced in the winding itil. This voltage is indicated, in terms of ground speed, by the meter |03;

With the rotor positioned as described, the motor shaft |89 is atan angle (0c-0) with respect to its reference position. The differential gear l il is rotated through this angle on one side by the shaft |139. The other side of the differential is rotated through the angle 6 by the shaft |53. The output shaft of the differential rotates through the sum of these'angles, Which is the angle a, and -operates the indicator ||5 to indicate heading.

As mentioned in connection with the description -o'f Figure r2, the input information may be supplied continuously, either manually or by automatic means rotating the vrange and lazimuth shafts, and thecurrent Aheading and ground speed information maybe simply indicated as described or may be `used to 2actuate other equipment.

The described invention affords accurate and relatively simple electrical systems for converting between one type of flight information, such as that provided by radar, to another type of information, such as that provided by airborne navigational instruments.

I claim as my invention:

l. In a flight simulator or the like, range and azimuth shafts to be drivenin accordance with respective positional coordinates, and respective motors coupled to said shafts; motor control means for each of said motors, each said control means being responsive to the magnitude and polarity of an electrical input thereto to energize the respective motor correspondingly for rotation in a corresponding direction; a source of voltage, and means for varying the magnitude of said voltage in accordance with the ground speed of 7,. the craft Whose night is to be simulated, a voltage divider device including an impedance element, ineans applying 'said voltage to said impedance element, and voltage pick-off means associatedwith said impedance element and movable with respect thereto, means for moving said voltage pick-off means according to the heading of the aircraft whose flight is to be simulated, and means coupling said azimuth shaft to said impedance device to move said impedance device to position corresponding to the azimuth angle, whereby the voltages at said pick-off means are proportional respectively to the radial and tangential components Vrespectively of said ground speed; means applying said voltage proportional to said radial component to said motor control means for said motor coupled to said range shaft; a resistor network including a variable resistor connected to said range shaft and a fixed resistor in series with said variable resistor and connected to said motor control means for said motor coupled to said azimuth shaft, and means` applying said voltage proportional to said' tangential component to said last-mentioned motor control means through said resistor network, the resistors in Said network being so proportioned that the voltage reaching said last-mentioned motor control means is substantially inversely proportional to range.

2. A fiight simulator system including means providing a voltage corresponding in magnitude to the ground speed of an aircraft whose flight is to be simulated, means including two relatively movable parts for resolving said voltage into two components proportional respectively to the cosine and to the sine of the angle between said parts, means responsive to said first-mentioned componentincluding a motor which runs at a speed proportional to said component and thus rotates through an angle proportional to the time integral of said component; means including Va voltage divider driven by said motor for dividing said second component by an amount proportional to said time integral, means including a second motor which runs at a speed proportional to said divided second component and thus rotates through an angle equivalent to the time integral of said divided second component, and means coupling said last-mentioned motor to said resolving means to rotate one of said parts thereof with respect to the other.

3. A flight simulator systemv including means providing a voltage corresponding in magnitude to the ground speed of an aircraft whose flight is to be simulated, means resolving said voltage into two components proportional respectively to the cosine and to the sine of the angle between the heading of said craft and the azimuth of said craft from a reference point; means integrating said first-mentioned component with respect to time, said means including a motor which runs at a speed proportional to said component and thus rotates through an angle proportional to the distance of said craft from said point; means including a voltage divider driven by said motor for dividing said second component by an amount proportional to said distance, means iritegratng' said divided second component with respecty to time, said last-mentioned means including a motor which runs at a speed proportional to said di: vided second component and thus rotates through an angle equivalent to the azimuth of s'aid craft from said point, and means' coupling said last# mentioned motor to said resolving means sup"-v ply said azimuth information thereto.

4. In a flight simulator or the like, range and azimuth shafts to be driven in accordance with respective positional coordinates, and respective motors coupled to said shafts; motor control means for each of said motors, each said control means being responsive to the magnitude and polarity of an electrical input thereto to energize the respective motor correspondingly for rotation in a corresponding direction; a source of voltage, and means for varying the magnitude of said voltage in accordance with the ground speed VG of the craft whose flight is to be simulated, a volt-age divider device including an impedance element, means applying said voltage to said impedance element, and voltage pick-off means associated with said impedance element and movable with respect thereto, means for moving said voltage pick-ofi means according to the heading a of the aircraft whose ight is to be simulated, and means coupling said azimuth shaft to said impedance device to rotate said impedance device to an angular position corresponding to the azimuth angle 0, whereby the voltages E1 and E2 at said pick-off means are proportional respectively to VG cos (a-) and VG sin (il-0) means applying said voltage E1, to said motor control means for said motor coupled to said range shaft; a resistor network including a variable resistor connected to said range shaft and a :fixed resistor in series with said variable resistor and connected to said motor control means for said motor coupled to said azimuth shaft, and means applying said voltage E2 to said last-mentioned motor control means through said resistor network, the resistors in said network being so proportioned that the voltage reaching said last-mentioned motor control means is substantially inversely proportional to range.

DOUGLAS H. EWING.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,116,508 Colvin May 10, 1938 2,366,603 Dehmel Jan. 2, 1945 2,404,387 Lovell July 23, 1946 2,406,836 Holden Sept. 3, 1946 2,416,363 Wellings Feb. 25, 1947 2,432,504 Baghosian Dec. 16, 1947 2,435,195 Bomberger Feb, 3, 1948 2,455,035 Bode Nov. 30, 1948 2,465,624 Agins Mar. 29, 1949 2,467,646 Agins Apr. 19, 1949 2,468,179 Darlington Apr. 26, 1949 

